Comparative tribo-dynamic studies of radial ball bearings possessing micro-grooved and conventional outer races, employing three different grades of lithium soap-based greases (NLGI grade 000, 2 and 3), are presented in this paper. This research has been conducted to explore and understand the effectiveness of grease grades on the performance parameters in the presence of a circumferential micro-groove on the outer race as compared to conventional case. Indication of lubricating film thickness formation (in terms of capacitance), frictional torque, vibrations, and rise in temperature have been assessed for the conventional and micro-grooved outer race bearings at different operating parameters ( pH = 0.9 to 1.4 GPa; speed = 1.4 to 4.2 m/s). The micro-grooved bearings (MB) provided the indication of better lubricating film formation in terms of capacitance reduction in the range of 11–19% as compared to the conventional bearing (CB) cases. However, the reduction in frictional torque, vibration and rise in temperature magnitudes have been found in the range of 14–26%, 6–23%, and 10–24% respectively, as compared to the CB cases.

For achieving improved lubrication in a radial ball bearing (BB1B 420206), a circumferential micro-groove inside the stationary outer race has been conceived based on finite element analysis to facilitate the availability of grease and to reduce the stresses at the contacts and it has been fabricated to conduct the experiments. To understand the effect of this micro-groove filled with grease on the film formation, frictional torque, and bearing dynamics, experiments were performed for measuring these variables at different operating parameters ( pH = 0.35–1.2 GPa; speed = 1.4–4.2 m/s). Capacitance based approach, load cell, and miniature accelerometer have been employed to measure the film thickness, frictional load and vibrations, respectively. The results achieved with bearings with micro-groove on outer races have been compared with bearings having the conventional races at the identical operating parameters. Reductions of 14%–41% in vibrations, up to 11.2% increase in film thickness (i.e. 11% reduction in the capacitance), and in the range of 15%–30% reduction in the frictional torque have been obtained as compared to conventional bearing cases.

A comparative study on fatigue life of deep groove radial ball bearings possessing conventional and micro-grooved outer races by experimental investigation is discussed in this paper. This research has been carried out to explore and understand the fatigue life of a micro-grooved ball bearing (MGB) with a circumferential micro-groove on outer race by conducting long duration tests under dry condition (i.e. wiping out the applied grease from the races by using tissue paper and lint free cloth) and compare the results with same size SKF BB1B 420206 conventional bearing (CB) at the identical operating parameters. Frictional torque (FT), bulk temperature, and overall vibration level of the test bearings (CB and MGB) at the maximum load zone have been measured at 800 N ( pH = 1.7 GPa) radial load and 1800 rpm (4.2 m/s) for the entire duration (7.8 million revolutions) of the experiments. Comparison of the surface conditions of the bearing components by means of the captured scanning electron microscope (SEM) images, roundness and deviation in profile of the races measured by co-ordinate measuring machine (CMM), and photographs captured before and after the experiment indicates lesser damage of the MGB components as compared to the conventional cases. Moreover, the initiation of fatigue failure in CBs is faster as compared to the MGBs for the same test condition, indicating longer bearing life in MGBs as compared to the CBs.